The University of Wisconsin-Madisen Arboretum produced this very nice leaflet: https://arboretum.wisc.edu/content/uploads/2012/11/35_ArbLeaflet.pdf.
It outlines how amphibians enhance ecosystem functions and enrich our lives and is largely based on our recent paper:
Hocking, D. J. and K. J. Babbitt. 2014. Amphibian Contributions to Ecosystem Services. Herpetological Conservation and Biology. 9(1): 1-17.
The paper is published as Open Access so anyone can read it regardless of affiliation and subscription if you’re interested in more details.